火邪者，谓其不当用火而用之，故谓之火邪。凡伤寒汗不出，服发汗药至于再三而汗
不行，此津液内涸也，其证故危。若寻常汗证，药未至切而汗不行，遽以火迫于床榻之下，
劫夺取汗，炎气熏灼，热邪交并，变为惊狂等证。实者，则烦躁不已，虚者，真阳脱亡，
当量其虚实而解散之。太阳汗下，心下痞，表里俱虚，复加烧刺，胸烦面青肤 者难治，
色黄手足温者可治。太阳中风，以火劫之，因火热两阳相结，熏灼发热于外，身必
发黄，热搏于内，则小便难。火热大甚，则手足躁扰，循衣摸床，为难治。小便利者，火
气未剧，尚可治也。
【凉血】太阳病，以火熏之，不得汗发，燥不解，必下清血，必为火邪，犀角地黄汤。
【发汗】脉浮，宜以汗解。用火炙之，邪无从出，病从腰以下必重而痹，名为火逆，
麻黄杏子薏苡甘草汤。
伤寒若吐不解，不大便五六日以上至十余日，日晡潮热，不恶寒，独语如见鬼状。
剧者则不识人，循衣摸床，惕而不安，微喘直视。若微者，发热谵语，大承气汤。若一
服而利即止，复看脉弦者生，涩者死。仲景云∶循衣摸床者不可治。
【下】大承气汤、小承气汤，可选而用之。
直视者，目睛不能转动也。水精为志，火精为神，心使之也。伤寒直视为邪气壅胜，
冒其真气，使神志不卫于心，精气不荣于目，则为直视，多不治也。衄家不可汗，汗则
额上脉紧，直视不能动。狂言直视则为肾绝，摇头直视则为心绝，皆脏气已脱也。直视喘
满不知人，下反循衣摸床者直视者死。
【下】其或目中不了了，睛不和，无表里证，大便难，身微热者，非直视，乃内实也，
急下之，大柴胡汤，大承气汤，选用之。
火邪，是指本不应使用火疗法却误用了，因此称为火邪。凡是伤寒患者汗不出，服用发汗药多次而仍无汗，这是体内津液枯竭的表现，病情因而危险。如果是寻常的汗证，药物尚未对症而汗未出，就急忙在床榻下用火烘烤，强行劫取汗液，火热之气熏灼，热邪交织，从而变为惊狂等证候。实证者，则烦躁不止；虚证者，真阳脱失亡散，应当衡量其虚实情况而予以解散治疗。太阳病经过发汗和攻下后，心下痞塞，表里俱虚，又加上烧针或艾灸，出现胸中烦闷、面色青黑、皮肤枯槁的难以治疗，面色黄、手足温暖的可以治疗。太阳中风证，用火法劫迫，因火热与风邪两阳相结，熏灼发热于体表，身体必定发黄；热邪搏结于体内，则小便困难。火热极盛时，则手足躁动不安，循衣摸床，属于难治之症。若小便利，说明火气不剧烈，还可以治疗。
【凉血】太阳病，用火熏法，不得汗出，燥热不解，必然导致下部出血（便血），这必为火邪所致，用犀角地黄汤。
【发汗】脉浮，适宜用发汗法解除。若用火灸法，邪气无从排出，病邪从腰以下必定沉重且麻木痹痛，名为火逆，用麻黄杏子薏苡甘草汤。
伤寒如果经过吐法仍未痊愈，不大便五六天甚至十余天，傍晚时分潮热，不怕冷，独自说话如同看见鬼怪一样。严重的则不认识人，循衣摸床，惊恐不安，轻微气喘，两眼直视。症状较轻的，发热谵语，用大承气汤。如果服一次药后大便通利就停止服药，再诊察脉象，弦脉者生，涩脉者死。张仲景说：循衣摸床者不可治。
直视，是指眼球不能转动。肾藏志，水之精为志；心藏神，火之精为神，由心所主宰。伤寒出现直视是因为邪气壅盛，蒙蔽真气，使神志不能护卫于心，精气不能荣养于目，从而出现直视，大多难以治愈。经常鼻出血的人不可发汗，发汗则额上脉搏紧绷，两眼直视不能转动。胡言乱语且直视则是肾气绝，摇头且直视则是心气绝，都是脏气已经脱失。直视伴喘满、不认识人，或者下部反而出现循衣摸床症状的，以及直视的，均为死证。
【下法】如果眼中视物不清，眼球不和，没有表证也没有明显的里证，大便困难，身体微热的，不是直视，而是内实，急需攻下，用大柴胡汤或大承气汤，选择使用。
Fire pathogen refers to the condition caused by the inappropriate use of fire therapy when it should not have been used. In cases of cold damage where sweating does not occur, and after repeated administration of diaphoretic medicines, sweat still fails to emerge, this indicates the exhaustion of body fluids internally, rendering the condition critical. If it is a common case of impaired sweating where the medication has not yet taken effect, and one hastily applies heat beneath the bedstead to forcibly extract sweat, the scorching heat will combine with the pathogenic heat, transforming into symptoms such as fright and mania. In excess conditions, there is incessant irritability; in deficiency conditions, the true yang qi escapes and perishes. One must assess the excess or deficiency and apply dispersing treatments accordingly. After sweating and purging in Taiyang disease, if epigastric fullness occurs with both exterior and interior deficiency, and moxibustion or burning needles are additionally applied, chest irritability, bluish complexion, and dry skin indicate a difficult-to-treat condition. A yellowish complexion and warm hands and feet indicate a treatable condition. In Taiyang wind-strike, if forced by fire therapy, the fire heat and wind pathogen (both yang) bind together, scorching and causing fever externally, leading inevitably to jaundice. If heat binds internally, urination becomes difficult. When fire heat is extreme, restlessness of the hands and feet, grasping at clothes, and touching the bedclothes occur, indicating a difficult-to-treat state. If urination is free, the fire pathogen is not severe, and treatment is still possible.
[Cool Blood] In Taiyang disease, if fumigation with fire fails to induce sweating and the dryness persists, lower bleeding (hematochezia) will inevitably occur. This is definitely due to the fire pathogen; treat with Xijiao Dihuang Tang (Rhinoceros Horn and Rehmannia Decoction).
[Induce Sweating] When the pulse is floating, sweating is appropriate for resolution. If moxibustion is used, the pathogen has no outlet, and the disease manifests as heaviness and numbness from the waist down, termed "fire reversal." Treat with Mahuang Xingzi Yiyi Gancao Tang (Ephedra, Apricot Kernel, Coix Seed, and Licorice Decoction).
In cold damage, if vomiting fails to resolve the condition, and constipation persists for five to ten days or more, with tidal fever in the late afternoon, aversion to cold absent, and solitary speech resembling hallucinations of ghosts: in severe cases, the patient loses recognition of others, exhibits grasping at clothes and touching bedclothes, fearfulness and unrest, slight panting, and fixed gaze. In milder cases, fever and delirium occur; treat with Dachengqi Tang (Major Order the Qi Decoction). If one dose results in bowel movement, stop administering it. Re-evaluate the pulse: a wiry pulse indicates survival, while a choppy pulse indicates death. Zhang Zhongjing stated: "Grasping at clothes and touching bedclothes is untreatable."
[Purgative Method] Dachengqi Tang (Major Order the Qi Decoction) and Xiaochengqi Tang (Minor Order the Qi Decoction) may be selected for use.
Fixed gaze refers to the inability of the eyeballs to move. The essence of water stores zhi (will), and the essence of fire stores shen (spirit), governed by the Heart. In cold damage, fixed gaze occurs because pathogenic qi is abundant and obstructs the true qi, preventing the spirit from guarding the heart and the essence from nourishing the eyes. This usually indicates an incurable condition. Patients prone to epistaxis should not undergo sweating therapy; if sweated, the pulses on the forehead become tight, and fixed gaze with immobility ensues. Delirious speech with fixed gaze indicates kidney exhaustion; head shaking with fixed gaze indicates heart exhaustion; both signify the collapse of organ qi. Fixed gaze accompanied by panting, fullness, and loss of consciousness, or lower body manifestations of grasping at clothes and touching bedclothes, or simply fixed gaze alone, all indicate death.
[Purgative Method] If the eyes appear dim and the pupils are unresponsive, without exterior or obvious interior signs, with difficulty in defecation and slight body heat, this is not fixed gaze but internal excess. Urgent purgation is required. Use Daichaihu Tang (Bupleurum and Rhubarb Decoction) or Dachengqi Tang (Major Order the Qi Decoction), selecting as appropriate.